1 /** 2 * Copyright (C) 2010 Google, Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.inject.persist; 18 19 import com.google.inject.Inject; 20 import com.google.inject.Singleton; 21 22 import java.io.IOException; 23 24 import javax.servlet.Filter; 25 import javax.servlet.FilterChain; 26 import javax.servlet.FilterConfig; 27 import javax.servlet.ServletException; 28 import javax.servlet.ServletRequest; 29 import javax.servlet.ServletResponse; 30 31 /** 32 * Apply this filter to enable the HTTP Request unit of work and to have 33 * guice-persist manage the lifecycle of active units of work. 34 * The filter automatically starts and stops the relevant {@link PersistService} 35 * upon {@link javax.servlet.Filter#init(javax.servlet.FilterConfig)} and 36 * {@link javax.servlet.Filter#destroy()} respectively. 37 * 38 * <p> To be able to use the open session-in-view pattern (i.e. work per request), 39 * register this filter <b>once</b> in your Guice {@code ServletModule}. It is 40 * important that you register this filter before any other filter. 41 * 42 * For multiple providers, you should register this filter once per provider, inside 43 * a private module for each persist module installed (this must be the same private 44 * module where the specific persist module is itself installed). 45 * 46 * <p> 47 * Example configuration: 48 * <pre>{@code 49 * public class MyModule extends ServletModule { 50 * public void configureServlets() { 51 * filter("/*").through(PersistFilter.class); 52 * 53 * serve("/index.html").with(MyHtmlServlet.class); 54 * // Etc. 55 * } 56 * } 57 * }</pre> 58 * <p> 59 * This filter is thread safe and allows you to create injectors concurrently 60 * and deploy multiple guice-persist modules within the same injector, or even 61 * multiple injectors with persist modules withing the same JVM or web app. 62 * <p> 63 * This filter requires the Guice Servlet extension. 64 * 65 * @author Dhanji R. Prasanna (dhanji@gmail.com) 66 */ 67 @Singleton 68 public final class PersistFilter implements Filter { 69 private final UnitOfWork unitOfWork; 70 private final PersistService persistService; 71 72 @Inject PersistFilter(UnitOfWork unitOfWork, PersistService persistService)73 public PersistFilter(UnitOfWork unitOfWork, PersistService persistService) { 74 this.unitOfWork = unitOfWork; 75 this.persistService = persistService; 76 } 77 init(FilterConfig filterConfig)78 public void init(FilterConfig filterConfig) throws ServletException { 79 persistService.start(); 80 } 81 destroy()82 public void destroy() { 83 persistService.stop(); 84 } 85 doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, final FilterChain filterChain)86 public void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, 87 final FilterChain filterChain) throws IOException, ServletException { 88 89 unitOfWork.begin(); 90 try { 91 filterChain.doFilter(servletRequest, servletResponse); 92 } finally { 93 unitOfWork.end(); 94 } 95 } 96 } 97